MAIDENHEAD : Outgoing UK Prime Minister Keir Starmer said on Tuesday that Britain would spend a "record" of almost £300 billion ($397 billion) over the next four years to modernise its armed forces in the face of rising threats.

Starmer, expected to leave office next month after losing the support of Labour members of parliament, announced an extra £15 billion for defence spending up to 2030 when he launched his long-awaited Defence Investment Plan (DIP).

The plan, due to be published later on Tuesday, will see increased money for drones and autonomous systems as the nature of modern warfare changes.

"This record investment puts the security of the British public first, transforming our armed forces and giving them the funding and equipment they need to fight and defend our nation," Starmer said.

The plan follows months of wrangling within the Labour government over the resources required to modernise Britain's fighting capabilities to counter greater aggression from countries such as Russia, and a less reliable United States.

Two defence ministers quit earlier this month in a row over the defence plan, including defence secretary John Healey who said it risked making Britain "less safe".

The resignations highlighted Starmer's weakening authority.

He announced on June 22 he was stepping down after MPs from his ruling Labour party switched their support to veteran politician Andy Burnham.

Burnham, the 56-year-old former Greater Manchester mayor, will take over as prime minister in mid-July if he faces no challengers for the Labour leadership.

Starmer has called the defence plan "game-changing investment".

"I am absolutely certain that this is the platform on which whoever comes after me can build," he told reporters on Tuesday.

- 'Hybrid' vessels -

The plan includes more than £5.0 billion for drones and autonomous systems over the next four years, the Ministry of Defence (MoD) said in a press release.

The investment will see capabilities ranging from "highly complex autonomous mine-hunting drones to small 'quadcopter' tactical drones, and low-cost 'kamikaze' one-way attack drones", the MoD added.

The wars in Ukraine and Iran have highlighted the increased use of war-fighting robots.

Ukraine uses roughly 200,000 drones a month to defend itself from Russia's invasion, while at the height of the US-Israel-Iran conflict 700 offensive drones were being launched per day, the MoD said.

US President Donald Trump has demanded that NATO members spend five percent of economic growth on defence by 2035 and become less reliant on Washington for security.

Starmer said the defence plan will take defence spending to 4.2 percent of gross domestic product.

The £15 billion uplift is well short of the £28 billion that military leaders previously said was needed.

The opposition Conservatives' defence spokesperson, James Cartlidge, said the plan was "too little, too late".

"The plan is now almost a year overdue and only being rushed through because Keir Starmer is desperate for a legacy," he added.

On Monday, the government announced that from the early 2030s Britain will replace its six ageing destroyer warships with at least six "hybrid" vessels that will "mix crewed and uncrewed capabilities".